154 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. V. 



of the Terai, at p. 378, Vol I., of his " Himalayan Journals/' Dr. Hooker 

 says : " The gravel beds extend uninterruptedly upon the plains for 

 fully twenty miles south of the Sikkim mountains, the gravel becoming 

 smaller as the distance increases." " Throughout its breadth this forma- 

 tion is conspicuously cut into flat-topped terraces, flanking the spurs of 

 the mountains, at elevations varying from 250 to 1,000 feet above the 

 sea." " In many places, especially along the banks of the great streams, 

 the gravel is smaller, obscurely interstratified with sand, and the flat- 

 tened pebbles overlap rudely, in a manner characteristic of the effects 

 of running water ; but such is not the case with the main body of the 

 deposit, which is unstratified and much coarser. The alluvium of the 

 Gangetic valley is both interstratified with the gravel, and passes into 

 it, and was no doubt deposited in deep water, whilst the coarser matter 

 was accumulating at the foot of the mountains." 



If the opinion be adopted that the strata of the plains have not been 



much reduced by denudation, our previous infer- 

 Gangetic, compared . 



with the superficial depo- ence regarding the superficial deposits of the duns 

 sits of the duns. . 



is strengthened, that they, lor the most part, 



belong to a more remote period of formation than the deposits of the 

 plains, and are more closely connected with the Sivalik period. The 

 boulder-conglomerate, and the other undisturbed deposits about Kungora, 

 in the Noon section, are more raised above the plains than the highest 

 point of these is above the sea-level, and I have seen no evidence for 

 supposing that their relative position has ever sensibly changed. We 

 must then suppose the dun-deposits to have been laid down about the 

 close of the Sivalik period, and probably more or less under local condi- 

 tions produced by the contortion of the Sivalik rocks. This last condition 

 is more apparent in the case of the inner duns of the western region : it 

 is only in the outer line of duns, — those of Dehra, Pinjore, and Una, — 

 that any difficulty is encountered in separating the superficial deposits 

 from the underlying disturbed strata. In the Nadaon dun, and in many 



